ES2769404T3 - Integrated 3-level elevator / inverter for DC sources network coupling, power generation plant and operating procedure - Google Patents

Abstract

A DC / AC converter for converting the DC power from a number of inductively connected generators (120) into AC power conforming to the mains to feed an electrical network (740) connected with a number of phases, each phase (L , L1, L2, L3) is assigned to an associated generator (120), comprising: - an intermediate circuit with intermediate circuit capacitor (100, 110) and a positive and negative intermediate circuit connection, and - a bridge (160 ) for each phase (L, L1, L2, L3) of the electrical network (740), the bridge (160) comprising: - a first switch (211, 231) that forms a switchable connection path between the connection (170) positive intermediate circuit and a corresponding phase terminal (180), - a second switch (212, 232) that directly connects a positive generator terminal (150) of the generator (120) associated to the phase and to the phase terminal (180) , - a third switch (213, 233) that directly connects a negative generator terminal (155) or of the generator (120) associated with the phase and the phase terminal (180), - a fourth switch (214, 234) that forms a switchable connection path between the negative connection (175) of the intermediate circuit and the terminal (180 ) of phase, - a first diode (221) that connects the positive connection (170) of the intermediate circuit to the positive generator terminal (150) of the generator (120) associated with the phase, and - a fourth diode (224) that connects the negative connection (175) of the intermediate circuit to the negative generator terminal (155) of the generator (120) associated with the phase.

Description

DESCRIPTION

Integrated 3-level elevator / inverter for DC sources network coupling, power generation plant and operating procedure

The invention relates to a DC / AC converter, an electric power generation plant and a method of converting DC (direct current) voltage into AC (alternating current) voltage to supply a single-phase or multi-phase electrical power network.

Obtaining electrical energy from renewable sources is becoming increasingly important. A renewable energy source is sunlight, convertible into a DC voltage through photovoltaic generators (PV generators). For this purpose, a plurality of solar modules are connected in series to form so-called chains that, if applicable, can also be connected in parallel with additional chains. Here, the length of the chains determines the achievable DC voltage.

In particular in the case of electric power generation plants that have powers that exceed one megawatt today, it is desirable to operate with high generator voltages, which corresponds to large chain lengths, in order to keep the flow currents. This reduces the expense on connections within the plant by virtue of relatively small line cross sections. At the same time, it is desirable to select a generator voltage so that the peak values of the line voltage are exceeded.

Since there is a frequent requirement within the electric power generation plant to adjust the value of the generator voltage before feeding it to the connected electrical network, in particular to increase the generator voltage to a voltage value of an intermediate circuit , plants often have a configuration in which a booster converter, an intermediate circuit and a converter bridge are connected in series. The losses of the individual components are added in this configuration.

Document US 2011/0080147 A1, for example, describes said inverter, which comprises an elevator converter, an intermediate circuit and a converter bridge, in which the intermediate circuit and the converter bridge are coupled to the generator through the elevator converter. Therefore, power from the generator is always transferred through the boost converter, leading to higher total losses.

Document US 2007/0273338 A1 describes an inverter with two DC / AC jumpers used alternately, in which a DC / DC boost converter is arranged before one of the DC / AC jumpers. Depending on the input voltage, the indirect or direct path can be used, thus minimizing losses. A disadvantage of the configuration arises from the large number of parts that are required, in particular switching elements.

DE 102006 010694 A1 discloses a configuration with a DC / AC bridge and a DC / DC step-up converter. Two additional switching elements are used to directly couple a DC source to the DC / AC jumper or to indirectly couple the DC source to the DC / AC jumper through the boost converter. Despite a reduced number of switching elements compared to the arrangement shown in US 2007/0273338 A1, a large number of switching elements is still needed.

It is therefore an object of the present invention to provide a DC / AC converter that can employ a relatively low number of switches to efficiently carry out a conversion of the energy provided by the generator into an AC voltage shaped electrical power network . It is an additional object to provide a conversion procedure and a power plant that shows the same advantages.

The object is achieved by a converter as claimed according to claim 1 or claim 7, the converter possibly being part of an electric power generation system as claimed in claim 8. A conversion method is described in The method of claim 14. Advantageous embodiments of the invention are described in the respective dependent claims.

According to a first aspect of the invention, a DC / AC converter for the conversion of DC energy from a number of generators inductively connected to the AC voltage-shaped electric power network for feeding into a power network connected to a number of phases, each phase being assigned to a generator, comprises an intermediate circuit with an intermediate circuit capacitor and a positive and negative intermediate circuit connection and for each phase of the electrical network, a bridge. Each bridge comprises a first switch that forms a switchable connection path between the positive intermediate circuit connection and a phase terminal, a second switch that directly connects a positive generator terminal of the generator assigned to the phase and the phase terminal, a third switch that directly connects a negative generator terminal of the generator assigned to the phase and phase terminal, and a fourth switch that forms a switchable connection path between the negative intermediate circuit connection and the phase terminal. Furthermore, the bridge comprises a first diode that connects the positive intermediate circuit connection to the positive generator terminal of the generator assigned to the phase, and a fourth diode that connects the negative intermediate circuit connection to the negative generator terminal of the generator assigned to the phase.

The switch configuration allows the generator inductors to be charged with the help of the generator current, thus implementing a step-up converter function so that the energy stored in the inductors can be used to charge the intermediate circuit or to feed the mains so that the intermediate circuit can operate with an intermediate circuit voltage that exceeds the generator voltage. Therefore, an inverter with a step-up converter function is implemented with only four switches.

In advantageous embodiments of the converter, the number of the phases is one or three.

In a further advantageous embodiment of the converter, each bridge is respectively connected to the intermediate circuit as a common intermediate circuit through the positive intermediate circuit connection and the negative intermediate circuit connection. Due to the common intermediate circuit, a power deficit of an individual generator can be compensated, allowing a uniform power output across all phases. In this case, it is possible to balance the energy between the phases in multi-phase systems, although each phase is associated with a corresponding generator.

In a further advantageous embodiment of the converter, at least one of the inductively connected generators comprises a first and a second inductance that are magnetically interlocked, the first inductance being connected to the positive generator terminal, and the second inductance being connected to the negative generator terminal . In this way, the energy can be effectively stored in the inductors. In a further advantageous embodiment of the converter, at least one of the generators is connected to one of the generator terminals through a reverse current diode. In this way, excessive compensating currents between generators are suppressed.

In further advantageous embodiments of the converter, the switchable connection path between the positive intermediate circuit connection and the phase terminal comprises the second switch, and a free-flowing diode is respectively assigned to each switch in the bridge.

According to a second aspect of the invention, a DC / AC converter for the conversion of DC energy from a number of generators inductively connected to the AC voltage-shaped electric power network for feeding into a power network connected to a number of phases, each phase being associated with a generator of the number of generators, comprises an intermediate circuit with intermediate circuit capacitor and a positive intermediate circuit connection and a negative intermediate circuit connection. For each phase of the electrical network, a bridge is provided to switch between a plurality of switch configurations. In a first bridge switch configuration, the generator terminals are interconnected and the intermediate circuit transmits energy to the electrical network. In a second bridge switch configuration, power from the generator is transmitted to the utility grid and the intermediate circuit balances the difference between the power provided by the generator and the power flowing into the utility grid. Again, a step-up converter function is implemented and the power deficit of a generator can be compensated for, allowing uniform power output across all phases.

In accordance with a third aspect of the invention, an electric power generation plant comprises a DC / AC converter as described above, to which a number of generators are inductively connected. Preferably, at least one of the generators is grounded, particularly with high resistance. More preferably, the generator is grounded through a grounded current monitor. In further preferred embodiments, each of the generators is grounded, and all of the generators are respectively directly interconnected at one pole. The same advantages are obtained as for the first and second aspects.

According to a fourth aspect of the invention, a method of converting a DC supply, provided by a generator inductively connected to a positive generating terminal and a negative generating terminal, into AC energy to supply an electrical power network at a phase terminal across a bridge with a positive intermediate circuit connection and a negative intermediate circuit connection, it comprises timed switching of the bridge between at least two bridge switch configurations. In at least a first switch configuration, the generator terminals are interconnected and the intermediate circuit transmits energy to the electrical network. In at least a second switch configuration, the energy from the generator is transmitted to the electrical grid, and the intermediate circuit balances the difference between the energy provided by the generator and the energy flowing into the electrical grid. The same advantages are obtained as for the first and second aspects. In an advantageous embodiment, the method comprises timed switching of the bridge between four configurations of the bridge switches. In the first configuration, the positive and negative generator terminals are interconnected and connected to the positive intermediate circuit connection and the phase terminal. In the second configuration, the positive generator terminal is connected to the phase terminal and the positive intermediate circuit connection, but is isolated from the negative generator terminal. In a third configuration, the negative generator terminal is connected to the phase terminal and the negative intermediate circuit connection, but is isolated from the positive generator terminal. In a fourth configuration, the positive and negative generator terminals are interconnected and connected to the negative intermediate circuit connection and to the phase terminal.

In further advantageous embodiments of the method, the power grid comprises three phases, each phase is associated with a bridge and a generator, the timed switching of the bridges is performed by a common control using delta modulation of sine wave or using a modulation of spatial vector, respectively. Both modulation schemes are suitable for precisely controlling the switches to provide network compliant AC voltage.

In a further advantageous embodiment of the method, timed switching between the first and second settings is performed at selected intervals to maximize the number of switches within the bridge that are being activated with the associated free-flowing diode that is in a conductive state. In this way, switching losses are minimized and maximum converter efficiency is achieved.

The invention is illustrated below with the help of figures which are to be interpreted as being explanatory but not restrictive. In the drawing:

Figure 1 shows a schematic diagram of a single-phase electric power generation system, Figure 2 shows a schematic diagram of two bridge configurations of the invention,

Figure 3 shows a schematic diagram of a three-phase electrical power generation system, Figure 4 shows an illustration of current paths within a bridge during a positive half-wave phase in different switch configurations,

Figure 5 shows a time profile diagram of currents within the bridge with an assigned sequence of bridge switch configurations.

Figure 6 shows a schematic of a three-phase electric power generation plant comprising a bridge in a first configuration of the invention, and

Figure 7 shows a schematic of a three-phase electric power generation plant comprising a bridge in a second configuration of the invention and with ground generators.

Figure 1 shows an illustration of an electrical power generation system comprising a generator 120. The positive pole of the generator is connected to a positive generator terminal 150 of bridge 160 through an inductor 130 generator and a reverse current diode 140 optional. The negative pole of generator 120 is directly connected to a negative generator terminal 155 of bridge 160 through a second generator inductor 131. The two inductors 130, 131 generators are magnetically interlocked. Alternatively, it is conceivable to provide only one of the two poles of generator 120 with an inductor, or not to inter-couple the two inductors magnetically.

The electric power generation system further comprises an intermediate circuit which is formed here as an intermediate circuit division comprising a first intermediate circuit capacitor 100 and a second intermediate circuit capacitor 110. The midpoint between the two intermediate circuit capacitors is connected to a neutral N conductor of a connected electrical network. The two intermediate circuit end points are connected to bridge 160 through a positive intermediate circuit connection 170 and a negative intermediate circuit connection 175. The bridge further comprises a phase terminal 180 through which a phase L of the connected electrical grid is connected through a filter comprising a grid inductor 190 and a filter capacitor 195.

Bridge 160 comprises a plurality of switches, and serves the purpose of interconnecting or isolating from each other in a time regulated sequence, the different connections through a plurality of switch configurations, in other words, a combination of the blocking states or conductivity of the switches contained in the bridge 160, making it in such a way that the electrical DC energy provided by the generator 120 is available at the phase terminal 180 as AC energy according to the electrical network.

Figures 2A and 2B illustrate two possible switch arrangements within bridge 160. In a first arrangement according to Figure 2A, bridge 160 comprises a first switch 211 which is connected at one end to the positive intermediate circuit connection 170 and , at the other end, both to the positive generator terminal 150 and to one end of a second switch 212. The other end of the second switch 212 is connected to the phase terminal 180, and to one end of a third switch 213. The third switch 213 It is connected at the other end to both the negative generator terminal 155 and one end of the fourth switch 214. The other end of the fourth switch 214 is connected to the negative intermediate circuit connection 175. The first switch 211 thus forms a switchable connection path between the intermediate circuit positive connection 170 and the phase terminal 180, the connection path in this case also including the second switch 212. The same is true for the connection path. switchable connection between the intermediate circuit negative connection 175 and the phase terminal 180 leading through the third switch 213. The individual switches can be formed of any type of known semiconductive switch, in particular semiconductor power switches such as MOSFETs, IGBTs, JFETs, and thyristors. Each switch can be assigned in this case a free-flowing diode 221,222, 223, 224.

Figure 2B shows a second switch arrangement that also comprises four switches. Here, the first switch 231 is connected with one end to the intermediate circuit positive connection 170, and with another end to the phase terminal 180. The second switch 232 is connected to operate with one end to the positive generator terminal 150 and is also connected to the phase terminal 180 with the other end. The third switch is arranged between the negative generator terminal 155 and the phase terminal 180, while the fourth switch is arranged between the negative intermediate circuit connection 175 and the phase terminal 180. The second switch 232 and the third switch 233 here also comprise parallel free-flowing diodes 222, 223. As shown, a first free-flowing diode 221 is arranged between positive intermediate circuit connection 170 and positive generator terminal 150, while a fourth free-flowing diode 224 is arranged between negative intermediate circuit connection 175 and terminal 155 negative generator. Of course, the first switch 231 and the fourth switch 234 may additionally comprise dedicated parallel free-flowing diodes (not shown).

In contrast to the arrangement of the switches of FIG. 2A, in the arrangement according to FIG. 2B a power provided through the intermediate circuit connections 170, 175 can be transmitted to the phase terminal 180 through a single switch 231, 234, while in the arrangement according to FIG. 2A, this energy flows through two switches 211, 212 or 213, 214. Therefore, a corresponding minimization of direct energy losses is possible.

Figure 3 shows an illustration, extended to use with a three-phase electrical network, of an electric power generation plant in the case where each phase L1, L2, L3 of the electrical network is respectively assigned to a bridge 160 to which in each case a corresponding generator 120 is connected inductively, that is to say through a generator inductor 130 or a pair of generator inductors 130, 131. Bridge 160 may be designed in accordance with one of the switching arrangements of Figure 2. The three bridges 160 are connected, both through their positive intermediate circuit connection 170 and through their negative intermediate circuit connection 175, to a common intermediate circuit which is configured here as a divided intermediate circuit with two intermediate circuit capacitors 100, 110 with connection of the midpoint to the neutral N conductor. Due to this connection, it is possible that the excess energy of the generators 120 is exchanged between the individual bridges 160 and, therefore, between the phases L1, L2, L3 of the electrical network in order to compensate for an energy deficit of one individual generator 120, thus allowing a uniform energy output through all three phases.

By way of example, in a variant of the invention, it is possible for this purpose to employ four different switch configurations in time sequence to implement a sinusoidal current profile to phase terminal 180. The four switch configurations are listed in Table 1 below. Here, 1 represents a conductive state of the respective switch S1, S2, S3, S4 and 0 for a blocking state. Switches S1, S2, S3, S4 correspond to switches 211, 212, 213, 214 or switches 231, 232, 233, 234 in Figures 2A and 2B. The last two columns of the table list the sign of the rate of change of the generator current iGen at one of terminals 150, 155 generators, and the sign of the rate of change of the phase current iNetz at terminal 180 phase.

Table 1:

The current paths in the case of the respective switch configurations according to table 1 are shown in figure 4 with the help of the switch arrangement of figure 2A in order to illustrate the operating mode of circuit 160 of bridge. In configuration 1, where the top three switches S1, S2, S3 of bridge 160 are in a conductive state, the line current at phase terminal 180 is provided through positive intermediate circuit connection 170, this is illustrated in section 401 of the current path. At the same time, the generator terminals 150, 155 are short-circuited through the switches S2 and S3, so that an electrical circuit 402 with an increasing current value is built through the generator 120 and the inductors 130, 131 generators.

In the case of a change in configuration 2, where only the top two switches S1, S2 are in a conductive state, electrical circuit 402 is interrupted by the opening of switch S3 so that the generator current is redirected along current path 412 at the phase terminal. A difference between the present generator current and the present phase current is balanced by a current flow 411 through the positive intermediate circuit connection 170 which, depending on the sign of this difference, can flow in both directions. The electrical circuit through generator 120 is closed by a corresponding current along current path 413 through intermediate circuit negative connection 175 and free-flowing diode 224.

In the third configuration, which corresponds to configuration 2 in a duplicate manner, the bottom two switches S3, S4 of bridge 160 are in a conductive state. Consequently, the generator current along path 421 flows through the free-flowing diode 221 and the positive intermediate circuit connection 170 to the intermediate circuit and, thereafter, through the negative circuit connection 175 intermediate back to the generator along current path 422. Furthermore, a current flows through the current path 423 towards the phase L of the electrical network so that, finally, the inductors 130, 131 generators are partially discharged in the intermediate circuit and partially in the electrical network.

In the fourth configuration, where the three lower switches S2, S3, S4 of bridge 160 are in a conductive state, a current is constructed in the same way in the generator electrical circuit 431, through the connection of the two terminals 150, 155 generators, while the DC link phase current is maintained along current path 432.

Configurations 1 and 4, where the generator inductors are charged with the help of the generator current, implement a step-up converter function such that the energy stored in the inductors can be used in configurations 2 and 3 to charge the intermediate circuit or it is supplied to the electrical network so that the intermediate circuit can operate with an intermediate circuit voltage that exceeds the generator voltage. By way of example, only specific changes between configurations may be allowed in one embodiment of a sequence of configurations during operation of the converter of the invention. Therefore, it is conceivable to operate the bridge only in a sequence 212343212343 ..., the dwell times in the respective configurations vary according to the control of the bridge within the period of one half line wave.

After changes between configurations, it is also possible to briefly adopt other switch configurations on the bridge, for example, because the instants of change between a conductor and a switch lock state may vary, and it must be ensured that There is no undesired short circuit of the bridge during switching. To this end, it is typical to use a dead time during bridge switching operations.

However, it is also conceivable to make deliberate use of other switch configurations in order to control the bridge. It can also be seen that various of the switching operations within the bridge can continue without loss, since the free-flowing diode assigned to the switch already carries a current at the switching time, so the switch voltage load is low in the switching instant. In order to maximize the efficiency of the converter, therefore, it is contemplated to switch between switch configurations or to select the subsequent configuration so as to maximize the number of switches activated at a time, in which the associated free-flowing diode is in a conductive state.

The time profile of the various currents on bridge 160 is shown in the form of a diagram in Figure 5 as a result of a simulation. Here, curve 510 shows the phase current profile compared to the sinusoidal current target value profile 500, and curve 520 shows the generator current profile. The ups and downs on curves 510, 520 are caused by the different switch settings of bridge 160, which are also shown as value stages of curve 530, and demonstrate how the bridge can simulate the target value profile 500 by A suitable change between switch configurations, the generator current assumes a profile 520 in a narrow region over a constant value, for example, the current in the MPP (Maximum Energy Point).

When the electric power generation plant is configured for power in multi-phase power grids, in an advantageous embodiment, the bridges assigned to the individual phases are operated, in particular whenever the intermediate voltage circuit is too low in comparison with the peak voltage of the electrical network, in such a way that a sine or delta wave modulation or a spatial vector modulation can be used. The neutral conductor potential N can therefore have a DC voltage component with respect to the earth potential, and / or an AC voltage component with triple line frequency.

Figure 6 shows an electric power generation plant according to Figure 3 for feeding a three-phase electrical network, bridges 160 being formed by a switch arrangement according to Figure 2B.

On the contrary, Figure 7 shows an electric power generation plant with a switch arrangement on bridges 160 according to Figure 2A, in this case the intermediate circuit being formed only by a single capacitor 100. In order to define the mean phase potential of phases L1, L2, L3, the latter are respectively connected through filter capacitors 750 to the positive and negative intermediate circuit connections. The electric power generation plant further comprises an AC disconnector 720, for example, a power grid protection, with which bridge 160 can be connected to a transformer 730 that converts the outgoing AC voltage to a suitable voltage value of the connected 740 electrical network. Transformer 730 can be, for example, a medium voltage transformer that allows the electrical energy generated by generators 120 to be directly supplied to a medium voltage electrical network. Furthermore, the electric power generation plant comprises a ground current monitor 700, for example a GFDI (Ground Fault Detection Interruption) which is respectively connected to one pole of each generator 120 of the electric power generation plant and monitors a current to a 710 ground connection and, when a permissible current value is exceeded, institutes appropriate measures, for example, isolates the plant from the electrical grid through the AC 720 disconnector. If the objective is to interconnect generators 120 assigned to different phases of the electrical network, for example in order to produce a ground reference, it is recommended to use reverse current diodes 140 in order to prevent excessive compensating currents between the generators 120.

Unlike what is shown in Figure 7, the ground reference can also be provided only for a single or a subset of the generators 120, and can also be designed with high resistance.

The invention is not limited to the described embodiments, which can be modified in various ways and supplemented by someone skilled in the art. In particular, it is possible that the mentioned characteristics are also designed in different combinations than those given, and that they are complemented with other previously known methods or components in order to implement the idea of the invention.

List of reference symbols.

100, 110 DC link capacitor

120 Generator

130 Generator inductor

140 Reverse current diode

150 positive generator terminal

155 Negative generator terminal

160 Bridge

170 Positive intermediate circuit connection

175 DC link negative connection

180 phase terminal

190 Mains inductor

195 Filter Capacitor

211, 231, S1 First switch

212, 232, S2 Second switch

213, 233, S3 Third switch

214, 234, S4 Fourth switch

221, 222, 223, 224 Free circulation diode

401,402, 411,412, 413, 421, 422, 423, 431,432 Current path section

500 Target value profile of phase current

510 Actual value profile of phase current

520 Generator Current Profile

530 Time sequence of bridge switch configurations

700 Ground Current Monitor 710 Ground Connection

720 AC Disconnector

730 transformer

740 Electrical network

750 Filter Capacitors N Neutral conductor

L, L1, L2, L3 Phase

Claims (16)

1. A DC / AC converter to convert DC power from a number of generators (120) connected inductively to AC power in accordance with the electrical grid to supply an electrical grid (740) connected with a number of phases, each phase (L, L1, L2, L3) is assigned to an associated generator (120), comprising: - an intermediate circuit with an intermediate circuit capacitor (100, 110) and a positive and negative intermediate circuit connection, and - a bridge (160) for each phase (L, L1, L2, L3) of the electrical network (740), the bridge (160) comprising: - a first switch (211, 231) that forms a switchable connection path between the positive intermediate circuit connection (170) and a corresponding phase terminal (180), - a second switch (212, 232) that directly connects a terminal (150) positive generator of the generator (120) associated to the phase and to the phase terminal (180), - a third switch (213, 233) that directly connects a negative generator terminal (155) of the phase associated generator (120) and the phase terminal (180), - a fourth switch (214, 234) that forms a switchable connection path between the negative intermediate circuit connection (175) and the phase terminal (180), - a first diode (221) connecting the positive intermediate circuit connection (170) to the positive generator terminal (150) of the generator (120) associated with the phase, and - a fourth diode (224) connecting the negative intermediate circuit connection (175) to the negative generator terminal (155) of the generator (120) associated with the phase. The converter according to claim 1, in which the number of phases is three and in which each bridge (160) is respectively connected to the intermediate circuit as a common intermediate circuit through the positive connection (170) of intermediate circuit and the negative intermediate circuit connection (175). The converter according to one of the preceding claims, wherein at least one of the inductively connected generators (120) comprises a first and a second inductance (130, 131) that are magnetically interlocked, the first being connected inductance (130) to the positive generator terminal (150), and the second inductor (131) being connected to the negative generator terminal (155). The converter according to one of the preceding claims, wherein at least one of the generators (120) is connected to one of the generator terminals (150, 155) through a reverse current diode (140). The converter according to one of the preceding claims, wherein the switchable connection path between the positive intermediate circuit connection (170) and the phase terminal (180) comprises the second switch (212). The converter according to one of the preceding claims, wherein a free-flowing diode (221, 222, 223, 224) is assigned to each switch in the bridge (160). 7. A DC / AC converter to convert DC power from a number of generators (120) connected inductively to AC power in accordance with the electrical grid to supply an electrical grid (740) connected with a number of phases (L, L1, L2, L3), each phase is associated with a generator of the number of generators (120), comprising: - an intermediate circuit with an intermediate circuit capacitor (100, 110) and a positive intermediate circuit connection (170) and a negative intermediate circuit connection (175), and - for each phase of the electrical network, a bridge (160) to switch between a plurality of switch configurations, in which in a first switch configuration of the bridge (160), the generator terminals (150, 155) are interconnected, and the intermediate circuit transmits energy to the electrical network (740), in a second switch configuration of the bridge (160), the energy of the generator (120) is transmitted directly to the electrical network (740) and a difference between the energy provided by the generator (120) and the energy flowing in the electrical network (740) is balanced by the intermediate circuit. 8. An electric power generation plant comprising a DC / AC converter as claimed in one of the preceding claims, to which a number of generators (120) are inductively connected. 9. The electric power generation plant according to claim 8, wherein at least one of the generators (120) is grounded. 10. The electric power generation plant according to claim 9, wherein one of the generators (120) is grounded with high resistance. 11. The electric power generation plant according to claim 9, wherein the generator (120) is grounded through a ground current monitor (700). 12. The electric power generation plant according to one of claims 9 to 11, wherein each of the generators (120) is grounded. 13. The electric power generation plant according to one of claims 9 to 12, in which all generators (120) are directly interconnected to one pole. 14. A method of converting a DC energy, provided by a generator (120) inductively connected to a positive generator terminal (150) and a negative generator terminal (155), into AC energy to supply a network (740 ) electrical at a phase terminal (180) through a bridge (160) with a positive intermediate circuit connection (170) and a negative intermediate circuit connection (175), comprising the timed switching of the bridge (160) between at least two switch configurations of the bridge (160), in which - in at least a first switch configuration, the generator terminals (150, 155) are interconnected, and the intermediate circuit transmits energy to the electrical network (740), - in at least a second switch configuration, the energy of the generator is transmitted directly to the electrical network (740), and a difference between the energy provided by the generator (120) and an energy flowing in the electrical network (740) it is balanced by the intermediate circuit. 15. The method according to claim 14, comprising four configurations of the bridge switches (160), wherein - in the first configuration, the positive and negative generator terminals (150, 155) are interconnected and connected to the positive intermediate circuit connection (170) and to the phase terminal (180), - in the second configuration, the positive generator terminal (150) is connected to the phase terminal (180) and to the positive intermediate circuit connection (170), but is isolated from the negative generator terminal (155), - in a third configuration, the negative generator terminal (155) is connected to the phase terminal (180) and to the negative intermediate circuit connection (175), but is isolated from the positive generator terminal (150), and - in a fourth configuration, the positive and negative generator terminals (150, 155) are interconnected and are connected to the negative intermediate circuit connection (175) and to the phase terminal (180). 16. The method according to claim 14 or 15, wherein the timed switching between the first and second settings is performed at selected intervals to maximize the number of switches within the bridge (160) that are activated by the free circulation that is associated in a conductive state.